Every one I've seen has circulation paths. They might not be obvious, but they are there.

Yes, natural convection will move the air around inside the chamber, that's not the issue. What you want to accomplish is to move the cold air from the fridge over to the chamber and return the warm air from the chamber back to the fridge. You need an in and an out path to accomplish this. It's a bit like putting your mouth on a plastic soda bottle and trying to blow into it - w/o a path for the air to escape, you don't really get any air movement. But put a hole in the other end, and the air moves right through.

It might be working because you get some initial movement and air flowing through leaks and some back through the fan once the pressures equalize. But I bet it runs out of 'gas' when it's more fully loaded, or the fridge might be called on to run too much (probably not, I just don't think you'll get enough air drawn away from the fridge).

Here's a thread with links to a classic design, the baffles, fan on one side, and port on the other provide the 'flow through' circulation.

Here's a simple approach - remove (or reverse) one of those two fans. Then add the tubing from that fan (or hole) to go down to the bottom of the chamber. That will force air movement through the chamber and back to the fridge. I really do think your results will be rather marginal w/o full circulation. It looks like a really nice build, I'd just like to see you get the most out of it.

-kenc

Thanks for the info. I'll definitely consider it. I understand you're saying about circulation, but there is one thing I don't understand, though. Why would I want to pull the air from the bottom of the chamber? That should be the coolest air in the chamber. If anything I'd think I'd want to pull the warmer air from the top out.

The only circulation I have is from the natural convection of cool air falling and warm air rising.

Quote:

Originally Posted by barryfine

Why would I want to pull the air from the bottom of the chamber?

That will give you the greatest convection and cooling power. Right now you're wasting energy, because the coolest air just sits at the bottom of the freezer, never moving since warmer air (from the top) is getting pulled, pushed to the top, and then falling through relatively warmer air back to the freezer. That's a bit of a simplification/exaggeration, but it seems pretty intuitive that to get the fullest flow of air, you want the stuff at the bottom of the freezer to get pulled to the top of the chamber.

That will give you the greatest convection and cooling power. Right now you're wasting energy, because the coolest air just sits at the bottom of the freezer, never moving since warmer air (from the top) is getting pulled, pushed to the top, and then falling through relatively warmer air back to the freezer. That's a bit of a simplification/exaggeration, but it seems pretty intuitive that to get the fullest flow of air, you want the stuff at the bottom of the freezer to get pulled to the top of the chamber.

I understand pulling the cold air to the top of the chamber, but he's suggesting pulling out the cold air from the bottom and putting it back into the freezer section. That sounds counter intuitive to me.

What he's suggesting is that you need a path for air to flow. When you push air into a chamber, you need somewhere for that air to go, or or it's like putting air in a tire. You're just creating air pressure which is most likely just pushing your cold air out of every crack that it can find. Convection alone is almost non-existent in your chambers unless your fans aren't running, also. The fans mix everything up quite well on their own, so nothing is really settling.

Ideally, you want to be able to push cold air in while giving a path for the warmer air to go back to the freezer to re-chill.

What he's suggesting is that you need a path for air to flow. When you push air into a chamber, you need somewhere for that air to go, or or it's like putting air in a tire. You're just creating air pressure which is most likely just pushing your cold air out of every crack that it can find. Convection alone is almost non-existent in your chambers unless your fans aren't running, also. The fans mix everything up quite well on their own, so nothing is really settling.

Ideally, you want to be able to push cold air in while giving a path for the warmer air to go back to the freezer to re-chill.

Yeah, I understand that, I was just confused why he thought I should I remove the air from the bottom of the chamber instead of from the top. I could easily just change the direction of one of the fans for the left section to get the kind of air flow you're talking about. His suggestion would require me to add a tube the left the section which would take up valuable real estate.

If both of your fans in the left section are blowing cold air in. I would definitely change the direction of one of them. You may also want to consider adding a tube on the freezer side of the fan blowing in the chamber that goes to the bottom of the freezer and sucks the cold air from there and see if that performs any better also.

As for the tube in the left section, you could probably do without it since the fan blowing in there is going to be enough to stir up any stratification that may exist.

If both of your fans in the left section are blowing cold air in. I would definitely change the direction of one of them. You may also want to consider adding a tube on the freezer side of the fan blowing in the chamber that goes to the bottom of the freezer and sucks the cold air from there and see if that performs any better also.

As for the tube in the left section, you could probably do without it since the fan blowing in there is going to be enough to stir up any stratification that may exist.

I already have tubes attached to the fans on the freezer section for both of those fans. I added those earlier this week and it really helped a lot.

I would just turn a fan around then, and take the tube off the freezer side of the one you turn around.
That should cool that chamber down a lot faster and make the whole system more efficient.

That's the kind of fix I like. Nice and easy. Unfortunately, trying to add circulation to the top chamber may prove to be more difficult. It would also take up space that I really don't want to give up. I think I'm going to see how it performs on a really hot day before I make any changes to the top chamber.

for the top chamber, you could try just putting another hole over your freezer. It's not ideal since the cold air will essentially settle and fall through it once the fan stops running. For this reason you probably wouldn't want it much bigger that your fan hole either. But it should work.

The real test will not only be a hot day, but when you have multiple beers in there bubbling away in primary fermentation. Those tend to heat up a chamber more than you'd think!